validation: Remove global ::PreciousBlock,ResetBlockFailureFlags

Summary:
Note: FinalizeBlock was already addressed in D6861

This is a backport of core#21055 [3/16]
https://github.com/bitcoin/bitcoin/pull/21055/commits/a3ba08ba7dec0b016e42233cd4a061ba1a0e86c1

Depends on D11206

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11207